Grid detection circuit for wave lengths below one decimeter



Aug. 10, 1937. HOLLMANN T 2,089,260 GRID DETECTION CIRCUIT FOR WAVELENGTHS BELOW ONE DECIMETE'R Filed Feb. 21, 1936 INVENTOR fi/AA/s ER/CHHOLLMAf/N WW5 m ATTORNEY Patented Aug. 10, 1937 are!) STATES PATENTOFFICE GRED DETECTION CIRCUIT FOR WAVE LENGTHS BELOW ONE DECIMETER tionof Germany Application February 21, 1936, Serial No. 65,002

In Germany 2 Claims.

By the development of special types of the audion or grid-detector tubethe inter-electrode distances have been reduced to microscopically smallproportions. It thus becomes possible to 5 use such a tube for wavelengths shorter than one decimeter without incurring any difiiculty dueto the electron transit times.

It will be understood that a receiver furnished with such a tube mustalso possess a circuit organization which is adapted to such extremelyshort waves. A circuit arrangement which has heretofore proved generallysuitable for ultrashort wave work and which has come to be known as theultra-audion scheme, I have found to be adapted also to decimeter waves.This circuit arrangement is in fact a three-point organization in whicha blocking condenser is connected in the node of the oscillation circuitinductance and serves to separate the plate potential from the gridpotential in series with the tube capacitance. This blocking condenser,therefore, serves for tuning, and at the same time as a grid condenser.

However, as soon as one gets into the range of half-meter Waves and usesshortinductance loops this difiiculty arises that the capacity of thetuning condenser cannot be made more than a few centimeters if thedesired wave is to be obtained. From the viewpoint of separating plateand grid potential, this is immaterial. But considering the function ofthe grid condenser, a greater capacitance is necessary in combinationwith the usual grid leaks in order to obtain the requisite smoothing ofthe potentials.

Now this difficulty is obviated by the present invention as follows:Although the capacitance of the tuning condenser is limited to a fewcentimeters, a fixed additional capacitor is connected in parallel. Thelatter is made of the required size of a grid condenser for obtainingsatisfactory rectification, say, a few hundred centimeters. In orderthat the said additional capacitor may not short circuit the tuningcondenser, and that it may not react upon the natural wave of the in- 45put circuit, the said two condensers must be isolated by high frequencychoke coils. The plate potential lead and the grid leak are connectedrespectively with one and the other of the two plates of the saidadditional capacitor.

The drawing shows a practical embodiment of the basic idea of theinvention in the form of a key diagram. R is the detector tube which,conjointly with the two inductance loops L1 and L2 and the seriescondenser C1 forms the receiving circuit to which the oscillationspicked up by March 6, 1935 2. suitable aerial are fed. In parallelrelation to the variable (tuning) condenser C1 is arranged the fixedadditional capacitor C2 being isolated for high frequency from condenserC1 by the aid of the two choke-coils D and D". 5

One plate is brought by way of the grid leak Rg to the cathode, whereasthe other plate is connected to the plate potential source Ea by way ofthe output transformer T. Regeneration may be insured in the customarymanner by variation of the cathode heating, of the plate potential, orelse of the damping of the oscillation circuit.

I claim:

1. A receiving circuit having means including an electron discharge tubefor rectifying ultrahigh frequency energy, said discharge tube having acathode, an anode and a grid so disposed in reference to one anotherthat the electron transit times are reduced to a minimum, a resonantcircuit including a distributed inductance and an adjustable midgetcapacitor intercoupling said anode and grid, an inductive and capacitivereactance offering a high impedance to said ultra-high frequency energyin shunt with said midget capacitor, a grid leak resistor in circuitbetween the cathode and grid by way of a portion of said inductivereactance, and an anode potential source in circuit between said cathodeand anode by way of another portion of said inductive reactance which isconductively separated from the first said portion by said midgetcapacitor and said capacitive reactance.

2. An ultra short wave receiving circuit arrangement comprising arectifier tube having a cathode, an anode, and a control grid, aresonant circuit, the terminals of which are connected respectively tothe anode and to the grid of said tube, said resonant circuit comprisinga lumped capacitance on each side of which is disposed a distributedinductance constituted by an arouateiy formed single conductor, a gridleak circuit connected between said cathode and through one of saidarcuately formed conductors to said grid, an anode-to-cathode circuitincluding an anode potential source and the other one of said arcuatelyformed conductors, and means including a condenser the capacitance ofwhich is large in relation to that of the capacitance in the resonantcircuit for smoothing the rectifier action, the first said capacitanceand the last said condenser being shunt-connected, and means forelectrically isolating said capacitance and said condenser at theoperating ultra high frequencies, said means comprising radio frequencychokes.

HANS ERICH HOLLMANN.

